Permanent transfer of art to objects, especially promotional objects, has been in existence for many decades. Because permanent adhesion is required, modern day decals used with or within promotional products are screen-printed. A traditional process for creating the decal applies the CMYK process, which is a subtractive color model used in color printing and also is used to describe the printing process itself. CMYK refers to the four inks used in the color printing: cyan, magenta, yellow and “key” (i.e., black).
In this standard printing process, color separations are generated for each color to be printed. FIG. 1, for example, shows a color separation display for a magenta negative of this four-color process. This means that, for every multi-color design, individual screens must be made for each color to be printed, which is a significant expense, and which is multiplied for each screen produced. FIGS. 2 and 3 show exemplary screens that are created by taking one of the various color negatives and exposing that negative design to an unexposed sheet of vellum to produce the actual, physical printing screen that is framed and then placed into a screen-printing press and used for transferring one of the colors to the object to be produced. To burn the negative onto the vellum, the vellum is first coated with a light-sensitive emulsion. The color separation pattern is exposed onto the vellum, resulting in a pattern that corresponds to that particular color needed to make the final artwork after all of the other colors are printed as well. Because each color and cover layer requires its own screen, there is a possibility that seven total screens need to be produced for any given artwork, one for white, four for each of the CMYK colors, one for a clear coat (e.g., as a protective layer), and one for a cover coat. Once all of the screens are produced for each of the colors, they can be used successively in a screen-printer to create a multi-color final printed decal, such as those shown in FIGS. 4 and 5. But the final printed decal is not created until every one of the independent color screens is used and individually printed with the respective color onto the decal base substrate.
A typical decal-creation process starts by printing a white base on the decal base substrate. One exemplary embodiment of the base substrate is white gum-coated paper, which is a material that allows the inks to first be printed thereon but later to slide off the base after being appropriately wetted. Such paper typically has a gum adhesive backing that allows one to create label products for a variety of purposes. Gummed paper requires water to activate the adhesive. Gummed paper is manufactured with a dry gum adhesive or a dextrin gum adhesive. Once the adhesive is activated, the paper will adhere to the item to be labeled. (Gummed paper is different from a pressure sensitive adhesive paper, which does not require wetting to activate the adhesive.)
As indicated above, for many applications (such as those shown in FIGS. 4 and 5), the decal has, as its first layer, a printing of white ink along the entire surface (or most of the surface) of the gum-coated paper. This white base ink layer must be allowed to dry completely before any other color can be printed on top of the white background so created. Each layer of ink is subsequently screen-printed, one color at a time, on top of the white base. Significantly, each ink layer must be allowed to dry individually, thereby, increasing production time and decreasing overall production throughput. The required drying between each color printing also increases cost. The second-to-last layer to be applied is a clear varnish that is used as a protective layer for the ink layers to increase scratch resistance and protect the colors. The last step of producing a prior art decal is to apply a clear overcoat. All of the ink printed prior to the cover coat adheres to the cover coat in this final printing step to produce a finished decal on top of the base substrate. In this way, the overcoat layer is used as a carrier for the ink layers so that, when the entire decal is wetted to activate the adhesive of the base substrate, the ink layers protected underneath the overcoat can slide off the base substrate. FIGS. 5 and 6 show an example of a finished decal on a base substrate with many different artworks printed one base substrate and FIG. 6 illustrates a base substrate on which is printed a white base layer, all of the color layers, the overcoat layer, and the cover coat. When created using this prior art screen-printing process, a decal is generated in hours, but it cannot be used for days due to the drying time that is required for the entire completed decal(s) sheet before transfer of the decal can be effected.
More specifically, the decal-containing base substrate needs to go through a number of post-printing processes. First, as shown in FIG. 7, each base substrate needs to be dried. Because the final decals are wetted in order to transfer them to the object, these substrates need to be completely dry before further processing of the decals can occur. This drying process takes a considerable amount of time, typically from four to eight hours. As multiple decals are present on a single decal-containing base substrate, processing efficiency requires the decals to be separated from other different decals by cutting, but only after many of the base substrates are layered together in a stack. Because the decals will be destroyed if the decal-containing base substrates stick to one another when placed in a stack, a slip-sheet (e.g., of wax paper) must be placed in between the adjacent sheets. This step is shown in FIG. 8, for example, in which a stack of decal-containing base substrates are separated with slip-sheets. Again, this post-processing step adds time, adds cost, and decreases production throughput. FIG. 9 shows the stack of decal-containing base substrates in an intermediate post-processing step where groups of decals 1 are separated from other groups of decals 1 or from individual decals 2. Such cutting typically takes place with a guillotine-type cutter 3. After cutting, as shown in FIGS. 10 and 11, the different projects are sorted, for example, for different customers.
The objects are, then, ready to be decorated with the respective decal(s). First, the decal is wetted. This moisture activates the adhesive supplied to the decal from the base substrate to permit the wet final sticker to slide off the base substrate and allow a human installer to place the wetted final sticker onto the object before the adhesive fully dries, at which time the decal can no longer be removed without destroying the decal or damaging the object, or both. In FIG. 12, for example, the object to receive a decal is a water bottle. The wetted decal is allowed to dry, typically, for approximately two hours. When dry, the installer is then able to and does peel off the cover coat, as shown in FIG. 13 in which the cover coat is partially peeled off. The object with the installed decal is then heated, as shown in FIG. 14, which heating permanently attaches the ink of the decal to the object's surface by removing all moisture and hardening the adhesive and/or ink. All totaled, previous prior art screen-printing processes—from first printing of the decal to a final product where the decal is permanently attached to the object—take four to six days to complete.
Digital print processes, as compared to screen-printed processes, print all colors at the same time in one pass. To date, digital printing processes have not been able to be used for decals, such as those for permanent attachment to objects, such as promotional materials. In particular, up until a few years ago, nothing was available. Further, LED-cured inks also were not available until about two years ago. Next, the right type of paper of digitally printing decals did not exist. While digitally printed labels existed, for example, in the food industry (labels on cans, food products, etc.), they were not resistant enough for promotional products. Accordingly, those of skill in the art have, to date, not been able to make digital printing processes work for these printing tasks. In fact, those of skill in the art have indicated that it is not even possible to print decals such as these with digital printers that print in one-step.
Thus, a need exists to overcome the problems with the prior art systems, designs, and processes as discussed above.